The present invention relates to a device and method for anastomosis of blood vessels.
In surgery, the term “anastomosis” is used to mean a connection made surgically between two hollow structures.
This invention relates in particular to end-to-side anastomosis, where an end portion of a blood vessel is connected to a side portion of a vessel wall.
This specification expressly refers to vascular anastomosis applied to the human body, without thereby restricting the scope of the invention.
The earliest method of anastomosing two parts of a blood or lymphatic vessel consists in suturing the free ends of the vessel with thread.
This method, commonly known as suture anastomosis, has several disadvantages, the main one being that the suture produces a scar which, however small, prevents original flow from being perfectly restored to the vessel.
In this regard, it should be stressed that blood vessels are made up of several layers. The first, innermost layer, called endothelium, is covered by a second, middle layer called tunica media. The tunica media is in turn covered by a third layer, known as tunica adventitia.
It is therefore relatively easy for suturing to cause misalignment of some kind between the layers of one end of the vessel and the corresponding layers of the end of the other vessel. This is also a drawback in the case of lymphatic vessels which have a similar layered structure.
A second drawback is due to the fact that blood vessel suturing must be done by hand by a specialized surgeon because it is a complex operation that cannot be left to surgeons who are not highly skilled in this specific art.
Another known method of anastomosing two parts of a blood or lymphatic vessel is to use mechanical clamping devices designed to turn the ends to be connected inside out and to then join the inside walls of the vessel ends to each other.
This surgical technique (mechanical anastomosis by eversion), although simpler than suture anastomosis, is even less effective in re-establishing flow to the vessel.
For example, in the specific case of blood vessels, only the intimal layers are in contact with each other.
Besides this, mechanical anastomosis by eversion has other serious drawbacks which may be dangerous to a patient's health.
One drawback is due to the fact that everting the vessel ends may cause the ends to break, especially in the case of vessels larger than 3 mm in diameter whose walls are hardened by arteriosclerosis.
Another complication, specific to blood vessels, is caused by the fact that the inside layers of the vessel ends, after being turned inside out and placed side by side, are no longer exposed to the blood flow and therefore tend to atrophy, which in turn leads to narrowing of the blood vessel and reduction of the blood flow through it. The smaller the diameter of the vessel being operated on, the more serious this problem is.
In other mechanical anastomosis methods (such as the one described in U.S. Pat. No. 6,652,540) the two ends of the vessels to be joined are not placed in contact and, instead, metallic components are left in contact with the blood flowing through the vessel.
This produces an extremely dangerous condition which exposes the anastomosis to risk of immediate occlusion caused by the formation of a blood clot and narrowing of the anastomotic lumen.
Indeed, it has been found that contact between metal and blood tends to cause stenosis, that is to say, abnormal narrowing of the blood vessel, which may lead to total occlusion of the vessel in a period of 6 months to 1 year.
Those in the art have proposed to overcome this problem by chemically coating the metals with anti-stenosis substances, that is to say, substances that inhibit occlusions.
This solution has, however, produced serious problems because in many cases, the chemically coated metal parts in contact with the blood favor the formation of thrombi and the onset of acute thromboses that come sharply to a crisis, exposing patients to the risk of heart failure and, in some cases, leading to death.
Another drawback of prior art anastomosis devices is the complexity of applying them, especially to the side portions of the vessel. This means that the surgical operation involved tend to be very long, placing the patient at risk not only on account of the technical difficulty of the operation itself but also because of the likelihood of infection which increases with the increased length of time during which the body organs are exposed to the environment.